This invention relates to new and useful oil in water emulsions and to the process for preparing these emulsions. More particularly, this invention relates to the use of a certain class of hexahydropyrimidines as asphalt emulsifiers. The class of hexahydropyrimidines useful in the present invention is advantageous in that it is liquid at room temperatures so as to enable easy handling of the emulsifiers by manufacturers of asphalt emulsions.
Asphalt finds use in a wide variety of applications, including for the paving of road surfaces and for the manufacture of water-proof coatings and protective coatings in general. Generally speaking, asphalt is employed in these applications mainly in the form of a liquid. It is usually melted by heating and applied as a molten mass (hot mix), and combined with volatile organic solvents or "cut backs" to provide liquid solutions of the desired viscosity. Asphalt is also emulsified with water and used in the form of liquid asphalt emulsions.
The so called rapid-set asphalt emulsions require certain special properties. Among the most important is a high viscosity combined with a low residue. Since asphalt emulsions are generally applied by machinery, it is important that the emulsion be of a high viscosity so that it will not flow from the pavement being treated. A sufficiently high residue content, the residue corresponding to the amount of asphalt in the emulsion, is necessary so as to provide for suitable adhesion of the aggregate that is applied to the asphalt. For example, the requirements for cationic emulsified asphalts of the rapid-setting type, according to the specification designated D-2397-79 by the American Society for Testing and Materials (ASTM), requires a minimum of 60% residue in CRS-1 rapid set asphalts and a minimum of 65% residue in CRS-2 asphalts. CRS-1 asphalt is suitable for surface treatment, penetration macadam, sand-seal coat, tack coat, and mulch, whereas CRS-2 is suitable for surface treatment, penetration macadam, and single and multiple coarse aggregate seal coats.
Hexahydropyrimidines are known in the art. For example, U.S. Pat. No. 2,535,747, issued to Glen H. Morey on Dec. 26, 1950, and entitled "Substituted Hexahydropyrimidines and Method for Producing Them", discloses certain hexahydropyrimidines as being useful in chemical intermediates, as for example in the preparation of wetting agents by converting them to the lauric or oleic salts or to quaternary ammonium salts. The reaction product with formaldehyde may also be used in the production of plastics, for example, by reaction with phenol. There is no disclosure of the use of these hexahydropyrimidines in asphalt emulsions.